1. Technical Field
The invention relates generally to orthopedic devices used in physical therapy and rehabilitation. More specifically, the invention relates to apparatus for effectuating passive movement of fingers on a human hand.
2. Description of the Related Art
A known rehabilitation type technique for joints following joint surgery is continuous passive motion ("CPM"). The use of CPM is also being examined for degenerative joint diseases, such as arthritis. Devices have been designed to impart passive motion to the joints of the leg and, in particular, with a focus on the knee joint.
It is a relatively new concept to apply CPM to the hand to cause articulatory movement of the fingers. Since the fingers involve a number of joints which all describe a differing path of motion, it is difficult to design a machine which causes controlled passive articulatory movement of the fingers about all three joints. In addition to movement of the joints, it is necessary to obtain movement of the ligaments, tendons, and other associated gliding soft tissues to keep them from adhering to bones and surrounding soft tissues. It is also difficult to design a machine which can be applied to all fingers of the hand, including the thumb, and can be applied to more than one finger at a time, and which is easily adjustable for use with hands of differing sizes.
In known CPM hand devices, finger movement is caused by a motor-driven rigid or semirigid cable attached to a fingertip. The motor is attached at the bottom of the wrist and the finger is moved in flexion and extension as the semirigid cable pushes and pulls the finger. Other devices produce a multiple change in the angle of a linear arm attached to a fingertip to forcefully flex and extend the digits. Finally, the hand may be strapped in the middle of an apparatus that has a series of tracks or a rotating arm linked to the tips of the fingers to cause flexion and extension motion.
These known devices either bend the fingers through the angulatory arch of the digits or forcefully manipulate the fingers first in one direction (e.g., flexion) and then in the other (e.g., extension) to cause direct motor-driven flexion and extension.